One means of establishing priorities for conservation is analysis of
the degree to which existing networks of protected areas are
representative of the full range of ecosystems and species. At the
national level, detailed ecosystem or vegetation classifications can
provide a basis for assessing the representativeness of the existing
protected areas network. Provided that the data are available it is
also possible to carry out a study of this nature on aglobal level. Up
until now the data were not available.

Several studies have highlighted the status of forest protection and
decline for particular regions using some version of ecological zones
(e.g. Lysenko et al., 1995, Mackinnon, 1996). Although the FAO have
compiled data on forest resources globally (e.g. FAO 1995), the
methodology used has differed between developed and developing
countries. A more uniform approach to the forests of the different
regions of the world is called for (Paivinen 1996). The World
Conservation Monitoring Centre (WCMC) recently produced an analysis of
protection of ecological zones in the tropics (Murray et al. 1996),
using the system of ecofloristic zonesdeveloped for FAO. In 1996
Iremonger et al. wrote a global analysis; the extent of current forest
cover in each ecological zone was determined and the protection of
that existing forest cover was assessed (FAO,1997). This latter study
was possible because WCMC had completed a digital map of the world's
forests at a clear enough resolution for the work. However, in the
study the forest was not subdivided into different forest types, and
an overlay of ecological zones coverages was used as a surrogate for
these. The assumption in that study was that vegetationoccurring in
different ecological zones belongs to different ecological types.

The present study builds upon the work carried out byIremonger et
al. (1997). The digital world forest coverage was subdivided into
different broad forest types, and the ecological zones coverages were
used as an overlay to define in even more detail the ecological
variants of each forest type. The differences in scales and
resolutions upon which the forest data sets and the ecological
zones data sets were based, meant that the results of combining zones
and forest types was not always meaningful. A more in-depth analysis
of the reasons for the results obtained would be very useful and
eliminate misleading combinations (e.g., thorn forest in the Tropical
wet ecological zone) that may seem like rare and unique forest
variants.